Pelvis part prosthesis

ABSTRACT

A pelvis part prosthesis comprises an essentially hemispherically-shaped shell portion provided with two formed appendices, each of which has a positioning aperture and two connection elements connected to the appendices, and each being provided with a pin inserted with a self-locking tight fit in the positioning apertures. The connection elements are preferably designed as curved plates. The material layer, adjacent to the residual bone material of the pelvis, of the aforementioned parts of the prosthesis, may be in the shape of an open-cell structure to allow the bone material to grow into said structure.

The invention relates to a pelvis part prosthesis for replacement of apelvis section in the area of the hip joint, comprising a shell portionfor reception of a hip joint ball and connection elements joined theretofor securing the prosthesis in the area of pubic ilium.

A pelvic section prosthesis which is constructed in accordance with amodular principle, is disclosed in the German specification as laid openDE No. - 28 09 556 B2. It comprises a substantially block-shapedprincipal member having a reception space for the hip joint socket andseveral connection surfaces provided with holes and several pin-shapedconnection elements, which are fastened in the holes on the one hand,and are connected on the other hand to the remanent pelvic bone materialof the patient.

The principal member of the prosthesis is a comparatively large blockmember since it has to have several holes for the pin-shaped connectionelements so that these elements may be secured in a selected holedepending on the conditions encountered with the patient. Furthermore,the connection elements inserted into the holes are fastened to theprincipal member by means of screws, for which purpose supplementaltapped holes have to be provided in the principal member. Although awhole prosthesis adapted in its configuration to the prevailingrequirements in accordance with the conditions encountered with thepatient may be put together with these prosthesis elements, thisprocedure is onerous and time-consuming, because the connection elementsare not as readily accessible with the principal member in the implantedcondition. If the prosthesis elements selected are assembled before theimplanting operation, an optimum position of the elements of theprosthesis with respect to each other and thus an optimum functionalityof the whole prosthesis in the body of the patient cannot always beassured. The reason is because the principal member is anchored on thepelvic bone material by means of at least three connection elements.With such connections, it is uncertain whether each connection elementcan be anchored reliably in the pelvic bone material because of itsunfavourable structure after bone resection. Furthermore, the tappedholes and the fastening screws represent a supplemental production costin the manufacture of the prosthesis.

The object of the invention consists in the improvement of anendoprosthesis of the kind defined in the foregoing which assures thatthe prosthesis may be implanted rapidly and in simple manner as well aswith the result of an optimum functionality in the implanted state.

The resolution of the problem derives from the endoprosthesis which andis characterized in that the shell portion has two integrally formedappendices comprising a reception bore in each case, and that theconnection elements joined to the appendices each have a pin and areinstalled with this pin in the reception bores in a self-locking tightfit.

In a preferred embodiment of the endoprosthesis according to theinvention, each tight fitting joint between the hemispherically formedshell portion and the connection elements consists of a taper joint. Themetal connection elements have spatially curved plate elementscomprising holes for connection by means of screws on the correspondingbone regions. The bone-side material layer of the shell portion as wellas of the connection elements may complementally be formed as anopen-celled structure for the growing-in of bone material.

The endoprosthesis according to the invention, whereof the parts areavailable in different sizes for utilization of an anatomicallyindividually adapted prosthesis, may be implanted rapidly with anuncomplicated manner, because the final immobilization of the connectionelements, may be performed by means of a self-locking tight fit withoutprotracted assembling operations and may in each case be carried out bymeans of a sharp blow. The prosthesis elements may furthermore beimplanted more easily in optimum manner as regards position based on nomore than two connection elements to allow easier alignment of the shellportion. Furthermore, the proposed prosthesis may be produced moreeconomically, since supplemental tapped holes with fastening screwsappertaining thereto for securing the connection elements are omitted inthe shell portion.

The invention is described in particular with reference to an example ofembodiment illustrated in the accompanying drawings. In these:

FIG. 1 shows the example of embodiment in sideview,

FIG. 2 shows a view of a first prosthesis element according to the arrowII in FIG. 1,

FIG. 3 shows a view according to the arrow III in FIG. 2,

FIG. 4 shows a partial cross-sectional view along the line IV--IV inFIG. 3,

FIG. 5 shows a sideview of a second prosthesis element of the example ofembodiment,

FIG. 6 shows a view according to the arrow VI in FIG. 5,

FIG. 7 shows another form of embodiment of the second prosthesis elementin sideview,

FIG. 8 shows a sideview of a third prosthesis element of the example ofembodiment,

FIG. 9 shows a view according to the arrow IX in FIG. 8,

FIGS. 10 and 11 show an alternative to the third detail in front andside view respectively,

FIG. 12 shows the example of embodiment according to FIG. 1 in theimplanted state.

According to FIG. 1, the endoprosthesis for replacement of a humanpelvic section in the region of the hip joint consists of severalinterconnectible principal components produced in a modular mode ofconstruction, that is to say, comprising a shell portion 1 for receptionof an artificial hip joint ball which is not shown, a connection element2 for fastening to the ilium and another connection element 3 forconnection to the os pubis.

The shell portion module 1 substantially comprises a hollow hemisphereof metal 4, for example high-grade alloyed steel with utilization ofchromium, cobalt and molybdenum, in which at least the layer of materialforming the external surface of the hemisphere may be formed as anopen-celled structure 5 for the growing-in of bone material. An equallyhemispherical socket 6 of plastics material, e.g. of polyethylene,whereof the cavity 7 receives an artificial hip joint ball (not shown)is anchored in the shell volume of the hemisphere.

The shell portion 1 has an appendix 8 and 9 formed integrally at each oftwo approximately mutually opposed points of its circumference, whichappendices are constructed for connection to the connection elements 2and 3, respectively. FIGS. 2,3 and 4 show enlarge details in thisrespect. It is apparent therefrom that the appendices 8,9 are formed byan one-piece casting, jointly with the hemisphere 4, the appendicesbeing formed in the manner of a pedestal bearing and each having areception bore 10 and 11 for reception of the corresponding connectionelement. The reception bores 10,11 are produced as tapered bores whichcooperate with tapered pins of the connection elements, as will bedescribed. The tapered reception bore 10 of the ilium-side appendix 8need not be made tapering throughout its length, but may also have acylindrical portion 12. As for the rest, the appendix 8 need notnecessarily be provided with an open-celled structure in the area of itssurface.

FIGS. 5, 6 and 7 show forms of embodiment for the connection elements 3at the side of the os pubis. The form of embodiment according to FIGS. 5and 6 comprises an elongated, spatially curved plate section 13 havingseveral holes 14,15 for connection by means of screws to the os pubis(FIG. 10). The hole 15 is formed as a slot to allow of setting up aprecise position of the connection element 3 on the os pubis before itis finally screwed tight. A taper pin which is driven into the receptionbore 11 of the appendix 9 of the shell portion 1, is provided at oneextremity of the plate section 13.

The connection element 3 described in the foregoing as well as theconnection element 2 according to FIG. 7, are formed from the samematerial as the shell portion. Furthermore, the boneside material layerof these elements may supplementally be formed as an open-celledstructure for the growing-in of bone material. These elements, exceptfor their pins 16, may alternately also be produced as elements havingan open-celled structure throughout.

The alternate connection element 3 according to FIG. 7 has a finger-likeprojection 17 of circular cross-section, with a mainly hemisphericalhead 18 at its one extremity, which bead carries the already referred topin 16 extending at right angle to said projection. Whereas thefinger-like projection 17 is implanted into a corresponding recess ofthe prepared os pubis, the tapered pin 16 engages in the taperedreception bore 11 of the appendix 9.

The connection element, according to FIGS. 8 and 8, produced from thesame material as the other elements 1 and 3. The connection elementcomprises an approximately triangular plate section 19 curved a littlespatially, comprising several holes 20 and a shank 21 which has a taper22 on its free terminal portion. Whereas the plate section 19 isfastened on the appropriately prepared ilium, the shank 21 engages withits taper 22 in the tapered reception bore 10 of the appendix 8 in apowerful friction lock (FIG. 1). The shank 21 extends over the platesection 19 at its rear side only, as shown in FIG. 8, so that the sideof the plate section 19 which is subsequently in contact with the ilium,is not covered by the shank material. This plate section 19 may alsoconsist of an opencelled structure, at least in its marginal layersubsequently facing towards the ilium; it may however also be made inthe form of an open-celled structure throughout.

Although it is preferable to join the connection elements 2 and 3 to theshell portion module by means of the tight taper fit shown anddescribed, it is also possible to utilize a gripping joint of the kindin which the gripping force is generated by means of screws, theappendices 8 and 9 then being slotted correspondingly for this purpose.

An alternative to the connection element 2 is shown in figures 10 and11. The plate section is formed as an L-shaped plate element 25, twobranches 25a and 25b thus produced extending approximately at rightangle to each other. The branches as such may be plane as shown, or mayalso be spatially curved. The shank 21 already referred to earlier inthe foregoing and comprising a gripping stud which is provided at theone side of the one branch 25a, whereas at least one projectinganchoring element 26 is provided at the other side of this branch.Several mutually spaced-apart anchoring elements 26 may also beprovided. As shown in FIGS. 10 and 11, the anchoring elements 26 whichis implanted in an appropriately prepared recess of the ilium, and thevertical branch 25b of the plate section 25, extend approximatelyparallel to each other. These parts may however also have a differentinclination with respect to each other, if the conditions imposed byanatomical or disease factors require this. When this alternateconnection element 2 is implanted, the ilium bears on the horizontalbranch 25a of the plate section 25 whereas the vertical branch 25b bearson the ilium laterally, as shown in broken lines in FIG. 12.

An uncomplicated form of embodiment of the anchoring element 26 consistsin that the shank 21 is produced with an upward extension. The branch25a then has a perforation 27 through which the shank 21 extends, theshank portion above the branch 25a forming the anchoring element. Inthis case, the shank is welded to the branch 25a.

Alternately, the plate section 25, the shank 21 and the anchoringelement 26 may also be formed as an one-piece casting.

In the case shown, the anchoring element 26 is cylindrically formed.However, it may have other cross-sectional shapes and other externalshapes. Further the bone-side marginal layer of the anchoring elementmay be produced as an open-celled structure for the growing-in of bonematerial, which may also be so in the case of the L-shaped plate section25. Alternately, and apart from the shank 21, this anchoring element mayalso be produced throughout as an open-celled-structure member. Finally,the plate section 25 is also provided with several holes 20 for itsattachment to the ilium.

FIG. 12 shows an implanted endoprosthesis of the kind described in theforegoing. After the diseased bone sections in the hip joint region ofthe pelvic bone structure have been removed according to the hatchedportion and the contact surfaces for the connection elements 2 and 3,i.e. for their plate sections 19 and 13 respectively have been preparedon the ilium 23 and the os pubis 24 respectively, the endoprosthesiswhereof the separate parts 1,2 and 3 may also be joined together thanksto previously performed determination of their individual size, shapeand reciprocal position, being screwed to the corresponding pelvic bones23,24.

It is apparent that the individual prosthesis elements may vary in theirshape and size to allow of utilization of the most suitable prosthesiselements and thus of the corresponding endoprosthesis in accordance withthe anatomical conditions of the hip joint region in question.

We claim:
 1. Pelvis part prosthesis for replacement of a pelvis sectionin the area of the hip joint of a human being, comprising a shellportion for the reception of an artificial hip joint ball and twoconnection elements mechanically joined to the shell portion forsecuring the prosthesis in the areas of the os pubis and the ilium,respectively, characterized in that the shell portion is formed as ahollow metal hemisphere having two outer integrally formed appendicesspaced about said hemisphere at positions near the os pubis and theilium, each having a conically formed reception bore, and that said twoconnection elements comprise metal plates which are formed such to adaptsecuring faces to remaining bone material of the os pubis and ilium,respectively, and which are provided with holes for receiving screws onsaid securing faces, and pin means having conically formed ends to besecured in respective conically formed reception bores of saidappendices by means of a self-locking tight fit.
 2. Pelvis partprosthesis according to claim 1, characterized in that said connectionelements consist of spatially curved metal plates.
 3. Pelvis partprosthesis according to claim 1, characterized in that the connectionelement to be secured to the os ilium is formed by an L-shaped metalplate, one branch of which is secured at the pin of said connectionelement such that a portion of said pin projects through said one branchand serves as an anchoring element, and the other branch of whichextends substantially parallel to said pin.